670
FXUS65 KBYZ 042023
AFDBYZ
AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE BILLINGS MT
223 PM MDT THU JUN 4 2026
KEY MESSAGES
- SOME THUNDERSTORMS MAY BECOME STRONG TO SEVERE IN SE MONTANA
AND NE WYOMING THIS AFTERNOON AND EVENING.
- MAIN THREATS WITH SEVERE THUNDERSTORMS TODAY ARE LARGE HAIL,
STRONG WINDS, AND HEAVY RAIN. SECONDARY THREAT IS ISOLATED
TORNADOES OVER FAR SOUTH-EASTERN MONTANA.
- ISOLATED TO SCATTERED SHOWERS AND THUNDERSTORMS SATURDAY WITH A
LATE TODAY COLD FRONT. A FEW THUNDERSTORMS MAY BECOME STRONG TO
SEVERE OVER EASTERN MONTANA.
- DAILY CHANCE OF SHOWERS AND THUNDERSTORMS CONTINUES SUNDAY INTO
NEXT WEEK.
UPDATE
UPDATED FOR SEVERE THUNDERSTORM WATCH NOW IN EFFECT FOR CUSTER,
CARTER, FALLON, AND POWDER RIVER COUNTIES UNTIL 9 PM THIS EVENING.
CHAMBERS
DISCUSSION
NEXT 7 DAYS...
THE MAIN STORY TODAY WILL BE THE POTENTIAL FOR SEVERE WEATHER
OVER THE EASTERN HALF OF THE CWA. A SHORTWAVE IS FORECAST TO MOVE
ACROSS ID/MT THROUGH THE DAY TODAY WHICH WILL BE THE PRIMARY
FORCING MECHANISM FOR CI THIS AFTERNOON. MOST HI-RES MODELS SHOW
AT LEAST SOME STORM INITIATION OCCURRING OFF OF THE PRYOR &
BIGHORN MOUNTAINS EARLY THIS AFTERNOON OUT AHEAD OF THAT FEATURE
IN THE AREA OF BROAD-SCALE DIFFLUENCE. THE MAIN DISCREPANCY
BETWEEN MODELS IS WHETHER OR NOT THESE STORMS WILL QUICKLY BECOME
STRONG OR NOT.
MORNING SURFACE OBSERVATIONS SHOW AN EASTERLY WIND THROUGH THE
EASTERN PORTION OF BYZ REACHING ROUGHLY TO THE BILLINGS AREA.
THIS HAS ALLOWED PWAT VALUES IN OUR EAST TO REMAIN AT LEAST 0.75"
WITH VALUES NEAR 1" ALONG THE MT/SD BORDER. ML CAPE VALUES THIS
MORNING, PER SPC MESOANALYSIS, SHOW VALUES OVER 500 J/KG IN SE MT
AND NY WY WITH ALL MODELS SHOWING VALUES OF 1000 TO 1500 J/KG BY
22Z TODAY. WHILE MODEST, THESE VALUES SHOULD BE ENOUGH TO SUPPORT
LOCALLY SEVERE CONVECTION. RAP AND NAM MODEL SOUNDINGS SHOW A
MODESTLY SUPPORTIVE ENVIRONMENT FOR SEVERE CONVECTION IN SE MT
THIS AFTERNOON AND EVENING. PROFILES OF LONG SKINNY CAPE WITH ELS
AROUND 250HPA, WHILE NOT EXPLOSIVE, WILL ALLOW FOR DEEP UPDRAFTS
TO BUILD WHILE EBWD VALUES OF AT LEAST 30KTS SHOULD PROVIDE
ENOUGH TILT TO THESE STORMS ALLOWING THEM TO POTENTIALLY SUSTAIN
THEMSELVES FOR SEVERAL HOURS.
HAIL APPEARS TO BE THE PRIMARY THREAT WITH ANY STORM THAT CAN GET
GOING TODAY AS FREEZING LEVELS ARE ONLY 8KFT AGL IN SOME
LOCATIONS WITH A -20C LEVEL OF ROUGHLY 20KFT AGL DEPENDING ON THE
MODEL. 40KTS OF WESTERLY FLOW THROUGH THE -10C TO -30C LEVEL WILL
BE SUFFICIENT ENOUGH FOR HYDROMETER SIZE SORTING AND THUS HAIL
GROWTH. THE LIMITING FACTOR WITH HAIL TODAY IS THAT MANY MODELS
ARE TRYING TO DEPICT THE ENTIRE ATMOSPHERIC COLUMN AS NEAR MOIST.
WHILE THIS SCENARIO WOULD LIMIT THE SIZE OF HAIL, IT WOULD NOT
LIMIT THE QUANTITY OF HAIL. LOOKING AT THE STRAIGHT LINE WIND
THREAT, THE LONG STRAIGHT HODOGRAPH DOES SUGGEST QUICK UPSCALE
GROWTH INTO A MULTICEL / LINEAR MODE OF STORMS. THE WINDS AT THE
SURFACE WOULD BE MOSTLY DEPENDENT ON WHETHER OR NOT A DECENT COLD
POOL AND/OR RIJ CAN SET UP AS 700HPA WINDS ARE NOT PARTICULARLY
STRONG (50KTS BY MOST MODELS). IN TERMS OF TORNADOES, THE THREAT
IS NOT ZERO. EFFECTIVE BULK SHEAR IN FAR SE MT AND EASTERN WY WILL
BE OVER 40KTS WITH LOCALIZED 50KTS DUE TO THE INCREASING LLJ
THROUGH THE EVENING. LOW LEVEL WINDS ARE FORECAST TO REMAIN DUE
EASTERLY THROUGH THE EVENING WHICH IS ROUGHLY 180 DEGREES OFF OF
THE MEAN SHEAR VECTOR (AND THEREFORE PROBABLE STORM MOTION) SO
EVEN AFTER THE STORMS DO GROW UPSCALE THERE IS A LOW PROBABILITY
OF A WIDELY ISOLATED BRIEF QLCS SPIN UP WHERE THE SPC HAS PUT A
2% TOR RISK. THE QUESTION IN THE NORTHERN HIGH PLAINS IN TERMS OF
TORNADOES IS ALWAYS THE LCL HEIGHTS AND WITH A GOOD MOISTURE RETURN
OUT OF THE RECENTLY SATURATED NORTHERN PLAINS THERE SHOULD BE NO
ISSUE IN KEEPING DEW POINTS IN THE LOW 50S F AND LCLS AROUND 1KM
AGL.
LOOKING AHEAD TO SATURDAY THERE IS ANOTHER CHANCE FOR SEVERE
WEATHER IN EASTERN MONTANA AS AN EVEN MORE POTENT SHORTWAVE
TROUGH MOVES THROUGH THE NORTHERN ROCKIES. THE SE SURFACE FLOW
WILL KEEP RETURN MOISTURE FLOWING IN ADDITION TO GOOD OVERALL
THETA-E ADVECTION KEEPING THE ATMOSPHERE READY TO KICK OFF
STORMS. AS THE FORCING APPROACHES DURING THE DAY SATURDAY
TEMPERATURES ARE ALSO FORECAST TO BE ABOVE AVERAGE WHICH SHOULD
AID IN RAISING SB CAPE VALUES. CLOUD COVER SHOULD BE LESS OF A
PROBLEM SATURDAY AS WELL DUE TO A WEAK RIDGE THAT BUILDS IN
TOMORROW AND THUS THERE SHOULD BE MINIMAL LINGERING CLOUDS
SATURDAY MORNING. LARGE HAIL AND DAMAGING WINDS WILL BE THE MAIN
THREAT SATURDAY AS THE WIDESPREAD HOT TEMPERATURES SHOULD RAISE
THE LCL ENOUGH TO KEEP TORNADOES A NULL THREAT, EVEN WITH A NICELY
HUMPED HODOGRAPH.
NEXT WEEK IT LOOKS LIKE THE PATTERN REMAINS ACTIVE WITH SEVERAL
MORE ROUNDS OF ENERGY MOVING ASHORE OFF OF THE NORTHERN PACIFIC.
DETAILS REMAIN FUZZY THIS FAR OUT SO BE SURE TO CHECK THE FORECAST
AS WE GET CLOSER AS THINGS COME INTO BETTER FOCUS. WMR
AVIATION
18Z DISCUSSION...THREAT TO AVIATION INTERESTS TODAY THROUGH
TOMORROW MORNING WILL BE SCATTERED CONVECTION THIS AFTERNOON
THROUGH THIS EVENING, AND FOG POTENTIAL IN THE SUNRISE HOURS.
ISOLATED MORNING CONVECTION OVER SE MONTANA WILL CONTINUE TO SHIFT
EASTWARD THROUGH THE EARLY AFTERNOON HOURS, POTENTIALLY BRINGING
SOME MVFR CONDITIONS TO KMLS/KBHK, ALONG WITH ISOLATED WIND GUSTS
TO 35KTS. SCATTERED SHOWERS AND STRONGER THUNDERSTORMS ARE
EXPECTED TO DEVELOP OVER CENTRAL AREAS OF THE FORECAST AREA (KBIL)
AROUND 20Z, AND SHIFT EASTWARD THROUGH THE EVENING HOURS.
STRONGER STORMS DURING THIS PERIOD MAY PRODUCE IFR CONDITIONS IN
HEAVY RAIN, ALONG WITH LARGE HAIL AND WIND GUSTS OVER 50KTS.
CONVECTION SHOULD EXIT TO THE EAST OF THE FORECAST AREA BETWEEN
05-07Z TONIGHT. BY THE EARLY MORNING HOURS, LOCATIONS THAT
RECEIVED SIGNIFICANT PRECIPITATION COULD SEE LOCALIZED FOG
DEVELOPMENT (IFR OR LOWER) LASTING UNTIL 16Z TOMORROW MORNING.
CHAMBERS
PRELIMINARY POINT TEMP/POPS
FRI SAT SUN MON TUE WED THU
-----------------------------------------------------------
BIL 052/088 057/087 055/071 046/080 055/083 054/079 052/074
20/U 00/B 25/T 31/B 11/B 45/T 54/T
LVM 044/085 049/084 047/067 037/074 045/075 044/070 041/065
20/U 02/T 37/T 41/B 12/T 47/T 66/T
HDN 048/088 054/090 053/073 044/082 053/084 052/081 050/075
20/U 00/B 15/T 40/U 11/B 34/T 54/T
MLS 050/085 058/092 057/075 047/079 057/085 057/083 055/076
40/U 00/U 32/W 41/U 21/B 22/T 53/W
4BQ 050/086 059/096 058/077 048/080 058/089 057/085 054/078
50/U 01/U 31/B 51/U 11/B 22/T 43/W
BHK 047/082 055/092 056/078 045/076 053/087 056/085 054/078
60/U 00/U 31/B 41/U 11/B 22/T 43/T
SHR 045/087 050/094 052/074 042/081 050/086 050/082 047/074
30/U 01/B 17/T 61/U 01/B 24/T 54/T
BYZ WATCHES/WARNINGS/ADVISORIES
MT...SEVERE THUNDERSTORM WATCH 272 IN EFFECT UNTIL 9 PM MDT THIS
EVENING FOR ZONES 32-33-36-37.
WY...NONE.
WEATHER.GOV/BILLINGS
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